The field of the invention is copolyamides of omega-aminocarboyxlic acids or lactams thereof with terephthalic acid or isophthalic acid and a diamine. The invention is particularly concerned with copolyamides of terephthalic acid and/or isophthalic acid or their esters or ester-forming derivatives and of diamine mixtures of isophorone diamine and bis-(4-aminocyclohexyl)-methane or derivatives thereof and omega-aminocarboxylic acids or lactams thereof having at least 11 C atoms.
Kirk-Othmer, "Encyclopedia of Chemical Technology", Vol. 16 (1968) discloses on pages 88-105 Polyamide Plastics and their types, processing, machining, finishing and assembly and the state of the art of copolyamides of lactams, dicarboxylic acids and diamines is disclosed in U.S. Pat. No. 3,627,736; French Pat. No. 1,471,798; Canadian Pat. No. 804,088; and British Pat. Nos. 1,132,039; 1,228,761; 1,266,864; 1,255,483; 1,410,006 and 1,410,007, the disclosures of which are incorporated herein. U.S. Pat. No. 4,101,524 is incorporated herein to show the state of the art of methods for preparing colorless polyester amides, the disclosure of which is incorporated herein.
The preparation of the amine raw materials of the present invention having the general formula ##STR2## is disclosed in the British Pat. No. 619,706.
Copolyamides of lactam, dicarboxylic acids and diamine mixtures in which isophorone diamine represents one component are known. Thus, French Pat. No. 1,471,798, British Pat. No. 1,132,039 and Canadian Pat. No. 804,088 disclose a copolyamide of aminoundecanoic acid, terephthalic acid and a mixture of diamines of isophorone diamine and dodecamethylenediamine. Such copolyamides however, are not satisfactory since they soften already at temperatures from 70.degree. to 80.degree. C. and hence lack adequate thermal dimensional stability. To achieve proper thermal dimensional stability, the state of the art attempts to minimize the proportion of lactams or aminoundecanoic acid. Thus, U.S. Pat. No. 3,627,736 and British Pat. Nos. 1,228,761; 1,266,864; 1,255,483; 1,410,006; and 1,410,007 disclose that this proportion should not exceed 20 mole % in the copolyamide. While it is possible in this manner to prepare transparent copolyamides with relatively high glass transition temperatures and hence good thermal stabilities, their melt viscosities are very high because of the low lactam or undecanoic acid proportions, whereby processing on conventional machinery is made considerably more difficult. If, however, the lactam proportion is raised to above 20 mole % in the copolyamides prepared in U.S. Pat. No. 3,627,736 and the British patents, a rapid decrease in the glass transition temperature takes place as shown in the comparative examples A and B which follow after the specific examples.
On the other hand, it is known that when isophorone diamine is used as the sole diamine component, copolyamides with high glass transition temperatures are obtained. However, copolyamides of terephthalic acid and/or isophthalic acid, isophorone diamine as the single diamine component and omega-aminocarboxylic acids or lactams having at least 11 C atoms can be condensed only into products of low molecular weights. Such products are brittle and offer no impact strength or notch impact strength as shown in comparative example C which follows the specific examples. These impact and notch impact strengths are determined according to German Industrial Standards DIN 53433 and DIN 54453.